This invention relates generally to electrical switching devices and, more particularly, to electrical switches that are capable of handling current transfers of up to, or greater than, 200 amps.
In North America, consumers coupled to the electric grid are supplied power with a 2-phase/180° supply. As inflation, as well as the cost of power generation has increased, the costs of supplying power to electrical consumers has also increased. Unfortunately for power distribution companies, the number of electrical utility consumers defaulting on their power bills has also increased. Often, the only recourse for a utility company is to shut-off the power to each defaulting consumer. Utility companies also selectively shut off electrical power to consumers, for a variety of other reasons, such as to enable maintenance to be safely performed.
To shut off the power to an electrical utility consumer, often the utility companies are required to dispatch at least one utility person to the site to disconnect that consumer from the electrical distribution grid. To enhance the power control capabilities of utilities, at least some utility revenue meters are equipped with an electrical switching element that works in cooperation with remote access and control capabilities integrated in the meter. Such electrical switching elements are generally placed in series between the meter and the electrical grid.
At least some known switching elements use some form of electromechanical, magnetically-latching, and/or electrically-controlled solenoid to open or close electrical switching contacts. Opening and closing the electrical switching contacts enables the electrical power supplied to the consumer to be selectively disconnected and/or reconnected. For example, U.S. Pat. No. 6,292,075 to Connell et al., describes a two pole contactor that functions with a solenoid plunger actuator to impart a switching force within the switching element.
Within known switching elements, to limit arcing during operation, the switching force must generally be of a sufficient magnitude to enable the electrical contacts to be rapidly closed or opened. However, although at least some known switching elements are described has having a full load current rating of at least 200 amps, it is not uncommon that such switching elements are derated for only being used with current ratings of 150 amps or less. One reason for such derates is that some of the known switching elements may overheat when operated at the full load current rating. Moreover, because of their internal design, at least some known switching elements have limited switching cycles that may limit their useful life.
For example, at least some known switching elements include copper conductor busbars that transmit the current through the device. To increase the manufacturers ability to use the same conductor buss in different switching element designs, and to minimize the number of switching elements used in the construction of remote meter reading systems, the cross-sectional areas of known copper conductor busbars has been decreased until a flexible, conducting hinge is defined within the busbar. In addition, within at least some known switching elements, such conductor busbars are fabricated with a generally long length that includes a plurality of bends formed between the ends of each busbar. As is known, heat rise within such switching elements is directly proportional to the level of current conducted through the switching device. As such, the reduced cross sectional area of such conductor busses may contribute to the overall switch heat rise. Moreover, the inclusion of bends within such busbars may also cause local thermal stresses to develop.
In addition, depending on the design of the solenoid in known switches, the amount of magnetic latching, i.e., the holding force, may limit the use of the switching element. For example, within at least some known switching elements, the holding force generated by the solenoid may not be sufficient to adequately control heat rise within the switching element during use. Depending on the level of heat rise, the accuracy of the associated meter may decrease.
Accordingly, there is a need for an electrical switching device that is capable of handling currents up to, or greater than, 200 amps and operating with improved heat rise characteristics. Moreover, there is a need for an electrical switching device that has improved performance reliability and is of a design that enables the switching device to be used with a plurality of different meters commercially available from a plurality of different manufactures, and with a plurality of different meter components, such as, but not limited to, extension collars and/or sockets defined within the meter.